Question

The reason that the allele acts as a dominant allele is that

- the mutant HD allele suppresses protein production from the normal HD allele.
- the HD mutation results in a protein that can damage nerve cells even in the presence of the normal protein.
- the normal HD allele does not normally produce a protein but the mutant HD allele does.
- the protein produced from the mutant HD allele is non-functional.

Answer 1

The dominant allele in Huntington's disease leads to a mutant protein that damages nerve cells, with symptoms not typically appearing until after reproductive age, allowing transmission of the allele to the next generation.

Step-by-step explanation:

The reason that the allele acts as a dominant allele is that the HD mutation results in a protein that can damage nerve cells even in the presence of the normal protein. This mutation leads to an abnormal protein with large repeats of amino acid glutamine, which is toxic to neural tissue and thereby causes the symptoms characteristic of Huntington's disease. Even a single mutant allele can result in the full-blown disorder, and this phenomenon can persist in populations because the onset of Huntington's symptoms is often delayed until after the reproductive age, allowing the dominant mutant allele to be passed on to offspring.